In a digital communication system, frequency selectivity and time fluctuation of a transmission line occur because of multipath fading caused by reflection of a transmission signal on a building or the like and Doppler fluctuation caused by movement of a terminal. In such a multipath environment, a reception signal is a signal interfering with a transmission symbol and a symbol that reaches after a delay time.
In such a transmission line having the frequency selectivity, a single carrier transmission system attracts attention in recent years to obtain a best reception characteristic (see, for example, Non-Patent Literature 1 below). In the single carrier (SC) transmission system, peak power can be reduced compared with an OFDM (Orthogonal Frequency Division Multiplexing) transmission system (see, for example, Non-Patent Literature 2), which is multiple carrier (MC) transmission.
In a transmitter that performs the SC transmission, for example, a multi-fading measure is taken by performing transmission explained below. First, after a PSK (Phase Shift Keying) signal or a QAM (Quadrature Amplitude Modulation) signal, which is a digital modulation signal, is generated in a “Modulator”, the digital modulation signal is converted into a time domain signal by a pre-coder and an IDFT (Inverse Discrete Fourier Transform) processing unit. Thereafter, as a multipath fading measure, a CP is inserted in a CP (Cyclic Prefix) inserting unit. The CP inserting unit copies a predetermined number of samples in the rear of a time domain signal and adds the samples to the top of a transmission signal. Besides, as multipath fading measure means, ZP (zero padding: zero insertion) for inserting zero in parts in the beginning and the end of data is performed.
To suppress transmission peak power, in the transmitter that performs the SC transmission, in general, DFT (Discrete Fourier Transform) processing is performed in the pre-coder.